DE2500453A1 - PROCESS FOR RECOVERING WORK LEAD - Google Patents

Description

DUISBURG COPPER HUT

Duisburg, January 6th, 1975 Process for the extraction of lead

The present invention relates to a method for obtaining Work lead from ores containing lead, intermediate and waste products, in particular from residues containing lead sulphate through leaching, precipitation and pyrometallurgical processing of the precipitate.

It is known to leach lead from residues containing this, for example from flue dust from pyrite roasting or from intermediate products from ore processing using sodium or calcium chloride solutions (DT. Note G 8372). The leaching of the mostly as PbSO. The lead present in the residues or dusts in hot, acidic chloride solution takes place with the formation of soluble chloro complexes, whereby more than 30 g / l Pb can be dissolved. The disadvantage here is that a higher concentration of SO. Ions in a sodium chloride solution reduces the Pb solubility as a lead tetrachloro complex, so that it is necessary to continuously discharge sulfate, for example as CaSO ₄ . For this purpose, the addition of CaCl ₀ in solid form or as brine is necessary if an economically and process-technically favorable NaCl circuit is used. This not only results in additional CaCl ₀ costs, but also, due to the dilution with CaCl ₀ sol, an increased NaCl expenditure.

It is also known to separate lead from such solutions by cooling, cementing or precipitating with alkalis, in which case, however, any silver that may be present with it is only partially precipitated. It is also known to react for recovery of lead to fire assaying paths from the precipitate the oxychloride with sulfuric acid -to lead sulfate, which can be conventionally sintered with lead ores and then melted in a shaft furnace lead to lead bullion. With this process, only limited amounts of lead sulphate can be processed.

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A direct pyrometallurgical preparation of lead oxychloride to lead has not yet become known. This is the subject of the present invention. It is characterized in that the lead or lead sulphate-containing materials are leached in a known manner by means of chloride solutions to form soluble lead chlorine complexes, lead oxychloride (about 3 Pb (OH) _or PbCl ₀ ) is precipitated from this solution with milk of lime, and the precipitate is precipitated with gypsum as a contamination, possibly after drying, pelletizing or similar preparations with the addition of lime, coal and iron above 800 ° C, preferably at 900 C, e.g. in a short drum furnace, reducing the melting, the work removes lead, returns the calcium chloride slag to the leaching stage and discards any iron sulfide.

The return of the CaCl _o slag produced during melting to the leaching process is particularly advantageous because firstly a waste product is expediently reused, secondly there are no costs for the otherwise necessary CaCl _o procurement, and thirdly those in the slag

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contained small amounts of lead, possibly by adding chlorine can be recovered and finally through the sulphate discharge in the form of gypsum a maximum solubility of the BIeichlorokomplexes is maintained in the chloride solution.

When lead is precipitated from lead sodium hydroxide solution containing sulphate with lime, part of the calcium is precipitated as a sparingly soluble sulfate with the lead oxychloride. The amount of gypsum in the precipitate is depending on the leading SO. content of the lead alkali and on the the addition of milk of lime causes a reduction in the solubility of gypsum in the lye. The gypsum content in the precipitated product can be reduced by an excess of calcium chloride be kept low during ore leaching and by discharging the gypsum with the leaded lye residue. To the Iron is advantageously added to the binding of the remaining sulphate sulfur in the lead melting process. The amount of iron added, e.g. in Form of chips or granules, depends on the calcium sulphate content of the precipitate, with an excess of about 10%, based on the Sulfur content, is appropriate. The resulting iron sulfide can easily be separated from the liquid lead and from the slag.

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The following examples are intended to illustrate the process according to the invention in more detail explain without, however, limiting it to this.

example 1

A PbSCK-containing fly ash was leached with hot, acidic sodium chloride-containing solution, filtered, the lead was precipitated from the lead lye by adding milk of lime to a pH of 8.5, filtered off and washed. The dry material contained: 64.6% Pb, 6.7 % CaO, 10.8% Cl and 11.7% SO ₄ .

The precipitated product was then mixed with 12% lime, 8 % ground coke and 4% iron powder, based on 100 parts by weight of dry material. This feed mixture was heated in a clay-graphite crucible in Tammannofen to 900 ⁰ C, cooled after one hour reaction time, the crucible and the Bleiregulus, a low iron sulfide amount sov / ie slag separated. From 0.5 kg of the lead precipitated product, 0.314 kg of industrial lead was obtained, with a lead content of 99.7%, and 122 g of CaCl ^ slag. The lead output is 97%. The slag with 4-5% Pb was used again as a calcium carrier in the ore leaching, the Pb being redissolved, for example by introducing chlorine.

Example 2

From a Pb / Ag-containing dissolution residue in which the metals were present as insoluble sulfates or chlorides, both Pb and Ag complex were dissolved by sodium chloride leaching. The SO. Ions were largely separated off as gypsum with the alkali residue due to an excess of CaCl _{2 in the chloride liquor.} By precipitating the lead with milk of lime at a pH value of up to 8.0 and the remaining silver that remained in solution with Na ₀ S or H ₀ S as Ag ₀ S, after filtering off and washing the precipitate, a silver-containing basic lead chloride was obtained with ( in dry material) 75.6% Pb, 0.7% Ag, 0.9% CaO, 11.8 % Cl and 1.6% SO ₄ . 0.5 kg of this material were mixed with 55 g of CaO, 40 g of reducing carbon and 4 g of iron powder, and the smelting reduction was carried out by heating to 900 ° C. with a residence time of one hour. 381.5 g of low-sulfur industrial lead with 369 g of Pb = 97.5% of the input and 3.5 g of Ag = 100% of the input were obtained as lead rule. The slag with small droplet-shaped iron sulphide inclusions resulted in 127 g of approximately the following composition: CaCl 85%, Pb 5% and Fe 3 %.

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Claims (1)

Claim 1 Process for the extraction of lead from lead-containing ores, intermediate and waste products, in particular from residues containing lead sulphate through leaching, precipitation and pyrometallurgical processing of the precipitated product, characterized in that the lead or lead sulfate-containing materials by means of chloride solutions in a known manner leaches out of this solution with the formation of soluble lead chlorine complexes lead oxide, the gypsum-containing precipitate, precipitates with milk of lime with the addition of lime, coal and iron, it melts at temperatures above 800 ° C, preferably at 900 ° C, and removes the lead, the calcium chloride slag returned to the leaching stage and discarded iron sulfide. Claim 2 Process according to Claim 1, characterized in that, when present of silver in the starting material after the lead oxychloride precipitation carries out a silver sulphide precipitation, e.g. with sodium sulphide and that precipitated silver sulfide in the following melting process into the lead transferred, whereby the sulfide sulfur is bound by the added iron will. 609829/0344